1. Field of the Invention
The present invention relates to hemming machines, and, more particularly the invention relates to a sheet metal hemming machine utilizing a vertically movable anvil supporting the sheet metal part to be hemmed to impact against stationary dies which are moved into and out of impacting position.
2. General State of the Art
Typically sheet metal hemming machines utilize hydraulic cylinders for imparting vertical movement to the impacting punch or anvil. The vertical movement provided by these cylinders is often erratic, slowing down operation and causing inaccuracies, particularly where multiple cylinders are used.
Another major problem with the use of hydraulic cylinders is inevitable leakage and the attendant mess created.
Commonly, the sheet metal workpiece is supported on a stationary platen with vertically moving punches providing initial bending or flanging and hold down and also providing cam actuation of horizontally sliding punches, often requiring complex operating mechanisms with relatively slow sequential operation. Pivoting die carriers are sometimes used to simplify overall design.